1. Field of the Invention
This invention relates to spherical metal powders suitable for use in metal injection molding, and to a method for producing such powders.
2. Description of the Prior Art
Of the powdered raw materials used for metal injection molding, powdered alloys are produced by water-atomization or gas atomization.
When a melt of metal or alloy is formed into particles by water in the process of water atomization, the melt is cooled very rapidly so that the particles formed have a non-spherical shape. Their tap density ratio is therefore only 40-46%, and they cannot be used as a raw material for injection molding unless a large amount of an organic binder is blended with them. However, when the blending proportion of an organic binder is high, a long debinding time is needed and problems such as blistering or distortion arise with considerable frequency during the debinding process.
On the other hand, in the case of a gas-atomized powder, the particles produced are perfect spheres so that their tap density ratio is of the order of 60% and a sufficient injection moldability can be ensured, even with a low blending proportion of an organic binder. However, in this case, there is no interaction at all between particles after the debinding process. Thus, the strength of the debound body is reduced. Further, the gas-atomized powder is also more costly to produce than the water-atomized powder.